1. Field of the Invention
The present invention relates to an auger type ice making machine capable of discharging the supplied water from the evaporator housing and washing the interior of the evaporator housing during halt of ice making operation of the machine.
2. Discussion of the Prior Art
Since an auger type ice making machine is designed for continuously forming ice crystals within the evaporator housing, the supplied water causes adherence of scales to the internal surfaces of the evaporator housing, resulting deterioration of the ice making performance, an increase of load acting on the auger and defacement of the support bearings of the auger shaft. To avoid such problems, a discharge pipe with a drain valve is connected to a bottom portion of the evaporator housing to discharge the supplied water therefrom when the ice making operation is halted for washing. However, if the extrusion head of the ice making machine is in an air-tight condition due to the ice compacted therein, sufficient ventilation at the upper end portion of the evaporator housing may not be obtained to cause insufficient discharge of the supplied water from the evaporator housing and insufficient supply of fresh water for washing. As a result, the washing effect becomes lower, and the interior of the evaporator housing is frozen in excess if the supply of fresh water is insufficient at restart of the ice making operation.
In Japanese Utility Model Publication 62-7980, there is disclosed an auger type ice making machine in which an electric heater is mounted on the outer surface of the evaporator housing at a place corresponding with the extrusion head to be energized when the supplied water is discharged from the evaporator housing for washing. In such a conventional ice making machine, a washing timer is provided to be closed at a predetermined time interval for opening the drain valve and energizing the electric heater for a predetermined time and to be opened for closing the drain valve and deenergizing the electric heater after lapse of the predetermined time. Under control of the washing timer, it is not necessary to maintain the electric heater in its energized condition at least during the latter half of the predetermined time. Accordingly, the energization time of the electric heater becomes too long to cause use less consumption of the electric power, and the evaporator housing is heated in excess to cause loss of the electric energy at restart of the ice making operation.
To avoid such a problem as described above, it has been proposed to open the drain valve and energize the electric heater when a stored ice detection switch has been opened by ice fully stored in an ice storage bin and to close the drain valve and deenergize the electric heater when the stored ice detection switch is closed. Under such control of the stored ice detection switch, however, the energization time of the electric heater is prolonged if the stored ice is not consumed for a long time. As a result, the electric power is consumed uselessly, and the evaporator housing is heated In excess to cause loss of the electric energy at the time when the stored ice detection switch is closed to restart the ice making operation. It has been also proposed to provide a manually operated washing switch which is arranged to open the drain valve and energize the electric heater when it has been operated. In this case, however, washing of the evaporator housing would not be effected if the user forgot to operate the washing switch.